Re: [FFmpeg-devel] [PATCH] libavfilter/vf_drawtext: add letter_spacing as an evaluated parameter

[Paul B Mahol <onemda@gmail.com>]

On Tue, Jun 20, 2023 at 4:27 PM Francesco Carusi <klimklim@tiscali.it>
wrote:

> You can find an overview of the changes here:
>
> https://github.com/yethie/FFmpeg/blob/master/drawtext/CHANGES.md
>
> and the new code here:
>
> https://github.com/yethie/FFmpeg/blob/master/libavfilter/vf_drawtext.c


This have been already merged, with some minor changes.


>
>
>
> On 19/06/2023 19:56, Mark Ren wrote:
> > Ah alright I see. When might that push come through and is there
> somewhere
> > I can look at the kind of changes in the meantime?
> >
> > On Mon, Jun 19, 2023 at 12:39 PM Paul B Mahol <onemda@gmail.com> wrote:
> >
> >>
> >> On Mon, Jun 19, 2023 at 6:34 PM Mark Ren <mark.ren77@gmail.com> wrote:
> >>
> >>> When enabled it will add pixels (or subtract if given a negative value)
> >>> between each letters,
> >>> set use_kerning to false,
> >>> and add the pixels to text_w.
> >>>
> >> Conflicts with big drawtext filter set that will be pushed soon.
> >>
> >>
> >>> Signed-off-by: Mark Ren <mark.ren77@gmail.com>
> >>> ---
> >>>   libavfilter/vf_drawtext.c | 24 ++++++++++++++++++++----
> >>>   1 file changed, 20 insertions(+), 4 deletions(-)
> >>>
> >>> diff --git a/libavfilter/vf_drawtext.c b/libavfilter/vf_drawtext.c
> >>> index 71ab851462..ec8313820d 100644
> >>> --- a/libavfilter/vf_drawtext.c
> >>> +++ b/libavfilter/vf_drawtext.c
> >>> @@ -183,6 +183,7 @@ typedef struct DrawTextContext {
> >>>       unsigned int fontsize;          ///< font size to use
> >>>       unsigned int default_fontsize;  ///< default font size to use
> >>>
> >>> +    int letter_spacing;             ///< letter spacing in pixels
> >>>       int line_spacing;               ///< lines spacing in pixels
> >>>       short int draw_box;             ///< draw box around text - true
> or
> >>> false
> >>>       int boxborderw;                 ///< box border width
> >>> @@ -208,6 +209,8 @@ typedef struct DrawTextContext {
> >>>       char   *a_expr;
> >>>       AVExpr *a_pexpr;
> >>>       int alpha;
> >>> +    char* letter_spacing_expr;      ///< expression for letter spacing
> >>> +    AVExpr* letter_spacing_pexpr;   ///< parsed expression for letter
> >>> spacing
> >>>       AVLFG  prng;                    ///< random
> >>>       char       *tc_opt_string;      ///< specified timecode option
> string
> >>>       AVRational  tc_rate;            ///< frame rate for timecode
> >>> @@ -237,6 +240,7 @@ static const AVOption drawtext_options[]= {
> >>>       {"shadowcolor", "set shadow color",     OFFSET(shadowcolor.rgba),
> >>>   AV_OPT_TYPE_COLOR,  {.str="black"}, 0, 0, FLAGS},
> >>>       {"box",         "set box",              OFFSET(draw_box),
> >>>   AV_OPT_TYPE_BOOL,   {.i64=0},     0,        1       , FLAGS},
> >>>       {"boxborderw",  "set box border width", OFFSET(boxborderw),
> >>>   AV_OPT_TYPE_INT,    {.i64=0},     INT_MIN,  INT_MAX , FLAGS},
> >>> +    {"letter_spacing", "set letter spacing in pixels",
> >>> OFFSET(letter_spacing_expr), AV_OPT_TYPE_STRING, {.str="0"}, 0, 0,
> FLAGS},
> >>>       {"line_spacing",  "set line spacing in pixels",
> >>> OFFSET(line_spacing),   AV_OPT_TYPE_INT,    {.i64=0},     INT_MIN,
> >>> INT_MAX,FLAGS},
> >>>       {"fontsize",    "set font size",        OFFSET(fontsize_expr),
> >>> AV_OPT_TYPE_STRING, {.str=NULL},  0, 0 , FLAGS},
> >>>       {"x",           "set x expression",     OFFSET(x_expr),
> >>>   AV_OPT_TYPE_STRING, {.str="0"},   0, 0, FLAGS},
> >>> @@ -812,7 +816,7 @@ static av_cold int init(AVFilterContext *ctx)
> >>>                          FT_STROKER_LINEJOIN_ROUND, 0);
> >>>       }
> >>>
> >>> -    s->use_kerning = FT_HAS_KERNING(s->face);
> >>> +    s->use_kerning = FT_HAS_KERNING(s->face) && !s->letter_spacing;
> >>>
> >>>       /* load the fallback glyph with code 0 */
> >>>       load_glyph(ctx, NULL, 0);
> >>> @@ -857,8 +861,9 @@ static av_cold void uninit(AVFilterContext *ctx)
> >>>       av_expr_free(s->y_pexpr);
> >>>       av_expr_free(s->a_pexpr);
> >>>       av_expr_free(s->fontsize_pexpr);
> >>> +    av_expr_free(s->letter_spacing_pexpr);
> >>>
> >>> -    s->x_pexpr = s->y_pexpr = s->a_pexpr = s->fontsize_pexpr = NULL;
> >>> +    s->x_pexpr = s->y_pexpr = s->a_pexpr = s->fontsize_pexpr =
> >>> s->letter_spacing_pexpr = NULL;
> >>>
> >>>       av_freep(&s->positions);
> >>>       s->nb_positions = 0;
> >>> @@ -903,13 +908,16 @@ static int config_input(AVFilterLink *inlink)
> >>>       av_expr_free(s->x_pexpr);
> >>>       av_expr_free(s->y_pexpr);
> >>>       av_expr_free(s->a_pexpr);
> >>> -    s->x_pexpr = s->y_pexpr = s->a_pexpr = NULL;
> >>> +    av_expr_free(s->letter_spacing_pexpr);
> >>> +    s->x_pexpr = s->y_pexpr = s->a_pexpr = s->letter_spacing_pexpr =
> >>> NULL;
> >>>
> >>>       if ((ret = av_expr_parse(&s->x_pexpr, expr = s->x_expr,
> var_names,
> >>>                                NULL, NULL, fun2_names, fun2, 0, ctx))
> < 0
> >>> ||
> >>>           (ret = av_expr_parse(&s->y_pexpr, expr = s->y_expr,
> var_names,
> >>>                                NULL, NULL, fun2_names, fun2, 0, ctx))
> < 0
> >>> ||
> >>>           (ret = av_expr_parse(&s->a_pexpr, expr = s->a_expr,
> var_names,
> >>> +                             NULL, NULL, fun2_names, fun2, 0, ctx)) <
> 0
> >>> ||
> >>> +        (ret = av_expr_parse(&s->letter_spacing_pexpr, expr =
> >>> s->letter_spacing_expr, var_names,
> >>>                                NULL, NULL, fun2_names, fun2, 0, ctx))
> < 0)
> >>> {
> >>>           av_log(ctx, AV_LOG_ERROR, "Failed to parse expression: %s
> \n",
> >>> expr);
> >>>           return AVERROR(EINVAL);
> >>> @@ -1525,6 +1533,9 @@ continue_on_invalid2:
> >>>           dummy.fontsize = s->fontsize;
> >>>           glyph = av_tree_find(s->glyphs, &dummy, glyph_cmp, NULL);
> >>>
> >>> +        /* letter spacing */
> >>> +        x += s->letter_spacing;
> >>> +
> >>>           /* kerning */
> >>>           if (s->use_kerning && prev_glyph && glyph->code) {
> >>>               FT_Get_Kerning(s->face, prev_glyph->code, glyph->code,
> >>> @@ -1539,7 +1550,12 @@ continue_on_invalid2:
> >>>           else              x += glyph->advance;
> >>>       }
> >>>
> >>> -    max_text_line_w = FFMAX(x, max_text_line_w);
> >>> +    s->letter_spacing = av_expr_eval(s->letter_spacing_pexpr,
> >>> s->var_values, &s->prng);
> >>> +    if (s->letter_spacing < 0) {
> >>> +        max_text_line_w = x+ s->letter_spacing;
> >>> +    } else {
> >>> +        max_text_line_w = FFMAX(x, max_text_line_w) +
> s->letter_spacing;
> >>> +    }
> >>>
> >>>       s->var_values[VAR_TW] = s->var_values[VAR_TEXT_W] =
> max_text_line_w;
> >>>       s->var_values[VAR_TH] = s->var_values[VAR_TEXT_H] = y +
> >>> s->max_glyph_h;
> >>> --
> >>> 2.40.1
> >>>
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